/* Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.activiti.engine.impl;

import java.io.Serializable;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Objects;

import org.activiti.engine.ActivitiException;
import org.activiti.engine.impl.context.Context;
import org.activiti.engine.impl.interceptor.Command;
import org.activiti.engine.impl.interceptor.CommandContext;
import org.activiti.engine.impl.interceptor.CommandExecutor;
import org.activiti.engine.query.NativeQuery;
import org.apache.commons.lang3.StringUtils;

/**
 * Abstract superclass for all native query types.
 *
 * @author Bernd Ruecker (camunda)
 */
public abstract class AbstractNativeQuery<T extends NativeQuery<?, ?>, U> implements Command<Object>, NativeQuery<T, U>,
        Serializable {

    private static final long serialVersionUID = 1L;

    private static enum ResultType {
        LIST, LIST_PAGE, SINGLE_RESULT, COUNT
    }

    protected transient CommandExecutor commandExecutor;
    protected transient CommandContext commandContext;

    protected int maxResults = Integer.MAX_VALUE;
    protected int firstResult;
    protected ResultType resultType;

    private Map<String, Object> parameters = new HashMap<>();
    private String sqlStatement;

    protected AbstractNativeQuery(CommandExecutor commandExecutor) {
        this.commandExecutor = commandExecutor;
    }

    public AbstractNativeQuery(CommandContext commandContext) {
        this.commandContext = commandContext;
    }

    public AbstractNativeQuery<T, U> setCommandExecutor(CommandExecutor commandExecutor) {
        this.commandExecutor = commandExecutor;
        return this;
    }

    @Override
    @SuppressWarnings("unchecked")
    public T sql(String sqlStatement) {
        this.sqlStatement = sqlStatement;
        return (T) this;
    }

    @Override
    @SuppressWarnings("unchecked")
    public T parameter(String name, Object value) {
        parameters.put(name, value);
        return (T) this;
    }

    @Override
    @SuppressWarnings("unchecked")
    public U singleResult() {
        this.resultType = ResultType.SINGLE_RESULT;
        if (commandExecutor != null) {
            return (U) commandExecutor.execute(this);
        }
        return executeSingleResult(Context.getCommandContext());
    }

    @Override
    @SuppressWarnings("unchecked")
    public List<U> list() {
        this.resultType = ResultType.LIST;
        if (commandExecutor != null) {
            return (List<U>) commandExecutor.execute(this);
        }
        return executeList(Context.getCommandContext(), getParameterMap(), 0, Integer.MAX_VALUE);
    }

    @Override
    @SuppressWarnings("unchecked")
    public List<U> listPage(int firstResult, int maxResults) {
        this.firstResult = firstResult;
        this.maxResults = maxResults;
        this.resultType = ResultType.LIST_PAGE;
        if (commandExecutor != null) {
            return (List<U>) commandExecutor.execute(this);
        }
        return executeList(Context.getCommandContext(), getParameterMap(), firstResult, maxResults);
    }

    @Override
    public long count() {
        this.resultType = ResultType.COUNT;
        if (commandExecutor != null) {
            return (Long) commandExecutor.execute(this);
        }
        return executeCount(Context.getCommandContext(), getParameterMap());
    }

    @Override
    public Object execute(CommandContext commandContext) {
        if (resultType == ResultType.LIST) {
            return executeList(commandContext, getParameterMap(), 0, Integer.MAX_VALUE);
        } else if (resultType == ResultType.LIST_PAGE) {
            Map<String, Object> parameterMap = getParameterMap();
            parameterMap.put("resultType", "LIST_PAGE");
            parameterMap.put("firstResult", firstResult);
            parameterMap.put("maxResults", maxResults);
            if (StringUtils.isNotBlank(Objects.toString(parameterMap.get("orderBy"), ""))) {
                parameterMap.put("orderByColumns", "RES." + parameterMap.get("orderBy"));
            } else {
                parameterMap.put("orderByColumns", "RES.ID_ asc");
            }

            int firstRow = firstResult + 1;
            parameterMap.put("firstRow", firstRow);
            int lastRow = 0;
            if (maxResults == Integer.MAX_VALUE) {
                lastRow = maxResults;
            } else {
                lastRow = firstResult + maxResults + 1;
            }
            parameterMap.put("lastRow", lastRow);
            return executeList(commandContext, parameterMap, firstResult, maxResults);
        } else if (resultType == ResultType.SINGLE_RESULT) {
            return executeSingleResult(commandContext);
        } else {
            return executeCount(commandContext, getParameterMap());
        }
    }

    public abstract long executeCount(CommandContext commandContext, Map<String, Object> parameterMap);

    /**
     * Executes the actual query to retrieve the list of results.
     *
     * @param maxResults
     * @param firstResult
     */
    public abstract List<U> executeList(CommandContext commandContext, Map<String, Object> parameterMap, int firstResult, int maxResults);

    public U executeSingleResult(CommandContext commandContext) {
        List<U> results = executeList(commandContext, getParameterMap(), 0, Integer.MAX_VALUE);
        if (results.size() == 1) {
            return results.get(0);
        } else if (results.size() > 1) {
            throw new ActivitiException("Query return " + results.size() + " results instead of max 1");
        }
        return null;
    }

    private Map<String, Object> getParameterMap() {
        HashMap<String, Object> parameterMap = new HashMap<>();
        parameterMap.put("sql", sqlStatement);
        parameterMap.putAll(parameters);
        return parameterMap;
    }

    public Map<String, Object> getParameters() {
        return parameters;
    }

}
